Elastomers are conventionally reinforced with dispersions of particulate carbon black and/or silica.
It is often difficult to obtain an adequate, heterogeneous dispersion of the silica in the rubber composition, due at least in part to the substantial tendency of the silica particles to agglomerate together to form "clumps" of silica which do not easily disperse within the rubber composition during the rubber/silica blending process under high shear conditions.
In the description of this invention, for convenience, articles and aggregates of silica and carbon black are used interchangeably. It is believed to be understood by those having skill in such art that particles of silica and of carbon black are usually present in a form of aggregates of individual primary particles thereof. Therefore, it is primarily the aggregates that tend to agglomerate together to form the "clumps" since the actual primary particles are normally only small portions of the silica and/or carbon black as the case may be.
In practice, rubber products such as tires are typically prepared of components such as, for example, treads of elastomer based rubber compositions which are conventionally carbon black reinforced. Sometimes tire tread rubber compositions may also be reinforced with silica by utilizing a combination of individual silica and carbon black particles. Typically, the silica is a precipitated silica.
Often coupling agents are used with precipitated silica to assist in its reinforcement of elastomers with which the silica is mixed. Utilization of silica couplers for such purpose is well known to those skilled in such art.
It is appreciated that adequate dispersion of the silica particles within the rubber composition is usually a concern.
In the description of this invention, the term "phr" where used herein, and according to conventional practice, refers to "parts of a respective material per 100 parts by weight of rubber, or elastomer".
In the description of this invention, the terms "rubber" and "elastomer" if used herein, may be used interchangeably, unless otherwise prescribed. The terms "rubber composition", "compounded rubber" and "rubber compound", if used herein, are used interchangeably to refer to "rubber which has been blended or mixed with various ingredients and materials" and such terms are well known to those having skill in the rubber mixing or rubber compounding art.